Attachment of hair springs to arbors



Patented Aug. 5, 194? ATTACHMENT OF HAIR SPRINGS TO ARBORS Ralph Roth Wentz, Brooklyn, N. Y.

Application December 2 7, 1938,. Serial No. 247,919

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to means for securing a hair spring to the escapement arbor in a, timin mechanism, and is especially adapted for use in the timing mechanism of time delay explosive missiles.

It is well known in the art of mechanical time fuses as distinguished from powder train fuses, that the timing mechanism generally resembles a watch mechanism in principle of operation, usually differing therefrom in the manner in which it is driven and in the escapement device.

The escapement differs from that of a watch, in that it is arranged to beat at a very much higher frequency and employs a hair spring capable of withstanding and properly functioning under greater shock and usage. A satisfactory spring for use in the escapement of the mechanical fuse is one of straight length and rectangular cross section or an elongated spring of similar cross section; however, the use of springs of the above types presents problems in regard to their attachment to the escapement arbor.

The general practice, heretofore, has been to insert the hair spring lengthwise through a hole of circular section drilled through the arbor spring to the arbor by inserting a circular wedge within the hole between the spring and defining surface of the hole. To obtain proper securement of the hair spring to the arbor it was necessary to so wedge that length of the spring within the hole as to deform it into a shape generally conforming to the radius of curvature of the hole. This practice results in the spring having a medial portion of arcuate section and end portions projecting from the hole of rectangular section, consequently upon fiexure of the spring in normal operation compound bends are developed in the spring at those points adjacent the arbor where the spring emerges from the hole in the arbor. The compound bends thus developed in the spring impose a severe strain thereon which rapidly fatigues the spring and may cause it to break rendering the fuse inoperative.

It is an object of my invention to so secure the hair spring to the arbor as to eliminate the introduction of compound bends of the above nature in the spring when it is flexed.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which- Fig. 1 is an elevation of the arbor assembly viewing the same in the direction of arrow A, Fig. 3;

Fig. 2 is a vertical section taken on the line 22 of Fig. 3;

Fig. 3 is a top plan view of the arbor assembly;

Fig. 4 is an elevation of the saddle used on the escapement arbor, and

Fig. 5 is a bottom plan view of the saddle shown in Fig. 4.

Referring to the drawings the escapement arbor to which the hair spring is to be affixed is shown at l. The arbor I may be of any suitable shape but as shown is an elongated, generally cylindrical member provided with bearing surfaces 2 and 3 at its opposed ends respectively, adapted to cooperate with suitable bearings for mounting the arbor for oscillatory movement.

Intermediate its ends the arbor l is provided with a diametral hole of such size as will permit the insertion of a hair spring 5 therethrough lengthwise with one of its transverse axes coinciding with the axis of the arbor.

To secure the hair spring to the escapement arbor l a saddle ii is used. The saddle 6 is generally U-shape in cross-section and in its cross web 1 is provided with an aperture 8 conforming in configuration with and adapted to be inserted over the main body of the arbor as shown in Fig. 2. The legs 9 and ll! of saddle 6 are each slotted at H and I2 respectively to permit the passage of the hair spring through the legs.

In the assembly of the elements of the escapement arbor the hair spring 5 is inserted lengthwise through the hole or opening t. The saddle 6 is then located on the arbor with its legs 9-40 directed downwardly as viewed in Fig. 2 and the slots ll, [2 engaging the hair spring as shown. The saddle is secured to the arbor by peening as shown at l3 or by other suitable fastening means as soldering, Welding, etc. To secure the spring to the saddle the saddle may be staked to the spring as indicated at I4 or otherwise secured by any well known expedient adapted to the purpose.

The method above described provides an expeditious, economical way of attaching the hair spring to the arbor without causing undesirable complex stresses to be set up in the spring while flexing and at the same time presents a desirable way of keeping the arbor balanced.

In accordance with the provisions of the patent statutes I have now particularly described the nature of this invention and the manner in which the same ma be employed and I claim and desire to secure by Letters Patent of the United States:

1. In an escapernent arbor assembly in combination, an escapement arbor adapted to be mounted for oscillation, provided with an opening passing therethrough transversely of and intersecting the axis of the arbor, an elongated hair spring passing through said opening lengthwise and means securing the hair spring to said arbor comprising a saddle having spaced legs provided with aligned slots engaging the spring on opposite sides of the arbor.

2. The structure recited in claim 1 wherein the saddle has a web transversely of the legs provided with an aperture through which the arbor extends in engaging relation and the arbor is peened to the Web around said aperture.

3. In an escapement arbor assembly in combination, an arbor provided with a hole extending therethrough transversely of and intersecting the axis of the arbor, an elongated hair spring extending therethrough transversely of and inter- REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,556,907 Bold Oct. 13, 1925 1,796,409 Schuler Mar. 17, 1931 20 2,281,494 Hammond Apr. 18, 1942 

